The present invention relates to an invisible, sealable, environmentally friendly, multilayer packaging material that acts as a good barrier to oxygen and moisture.
In the packaging industry, it is conventional to package products in a cardboard or a paper box. For some applications, cardboard or paper may be preferred to plastic for their rigidity for instance. They are also good support for printing and they are easy to recycle. Cardboard and paper are perfect when the packaged item is inert vis-à-vis the outside environment. But they usually do not act as barriers against oxygen, water vapor, odors or any other gases or liquids.
To avoid undesired conditions such as odors, gases or liquids passing from the packaged item to the outside and vice-versa, when the packaged item is food for instance, the cardboard packaging is usually covered by a polymeric plastic film or has a separate polymeric film sealed around the contents and inserted into the cardboard packaging. This plastic film (for example, polyvinylidene chloride) acts as a barrier against these substances. This tends to increase the number of packaging items used.
Nowadays, people are increasingly concerned about the environment and desire to take steps to preserve it for the future. Some governments have taken measures against the accumulation of packaging materials in landfills. In particular, using recyclable raw materials is strongly recommended whereas using non-recyclable polymeric substances is discouraged. Consumers are also encouraged to sort out the recyclable materials from the non-recyclable ones each time that they wish to dispose of used packaging materials in their everyday life. These operations require time and effort and new packaging products that are easier to sort out and to recycle are desired.
In order to have simple and less polluting packaging products, it would be desirable to combine into a single item both the cardboard and plastic film such as described above. A single piece package would be easy to remove, easy to transport and easy to recycle.
Also, because cardboard is naturally easier to recycle than polymeric substances, it would be desired to provide a combined packaging product having such a little percentage of polymers that it could still be considered, at least for some governmental recycling regulations, as a xe2x80x9cplainxe2x80x9d cardboard item and could therefore undergo the normal process stream for recycling of cardboard alone. At the same time, the barrier properties of the packaging, as well as its classical properties, like sealability, resistance, should be preserved.
In general, packaging films comprise a sealant layer which is sealed on itself, in order to ensure a safe closing of the packaging. The sealant layer is the topmost layer of the film and is usually in direct contact with the packaged item. In this view, the seal must possess a mechanical resistance sufficient to maintain the tight-seal properties during storage and transport.
In the case of food packaging in particular, it is important that the packaged food retain the integrity of its taste and odor during storage. To do this, the sealant layer should have good organoleptic properties and should not capture the food specific taste and odor. It is also very important that the taste and odor of the food are not altered, either by addition or by scalping, by the sealant layer. In addition, it is important that the packaging film has good barrier properties against oxygen and moisture or water vapor to preserve the goods over a long period of time.
EP 0 520 767 discloses a laminate material comprising an amorphous nylon layer applied to the inner surface of a paperboard substrate and a polyolefin layer in contact with the product. These kinds of materials are still not satisfactory as regards the preservation of the taste and odor of the packaged food and as regards sealability.
Therefore, there is still a need for a board-based packaging that would be effective as a barrier against oxygen and water vapor, that would preserve the taste and odor of the packaged item, that would be heat sealable and that could nevertheless be considered as a xe2x80x9cplainxe2x80x9d board item for recycling purposes.
Now, it has been surprisingly found that it is possible to co-extrude a particularly thin (preferably about 5 to about 100 microns and more preferably about 10 to about 30 microns) polymeric film having good barrier properties and to coat it onto a board or paper substrate in order to produce a board- or paper-based packaging product having good barrier properties against oxygen and water vapor and that could also be considered as a mono-material-based packaging for recycling purposes.
An aspect of the invention is a multilayer packaging comprising:
a) at least one cellulosic fibrous material substrate such as cardboard or paper, and
b) at least one polymeric film coated on the substrate of a), the polymeric film comprising:
i) at least one barrier layer comprising an olefin polymer, and
ii) at least one sealant layer comprising an amorphous polyamide, the sealant layer being in contact with the packaged product.
Although the packaging of the invention comprises only a little amount of polymers, it still has excellent barrier properties to oxygen and water vapor. Because of the specific nature of the sealant layer, the packaging has a good sealability on itself, which is important to maintain the packaging integrity, and it also shows good organoleptic properties. Food packaged in the package of the present invention does not lose its taste nor its pleasant odor. The film of the invention has no influence on the taste and odor of the packaged food. The packaging of the invention is environment friendly. Because of its low amount of polymers, it can be considered as xe2x80x9cpolymer-freexe2x80x9d according to the environment regulations standards of many countries and is easily recyclable. It is also easy and inexpensive to produce.
Moreover, because of the nature of the various polymers used in the packaging of the invention, the polymeric film is transparent. As such it is invisible to the customer, thus providing a packaging material that has the appearance of board or paper as if there was no polymeric film at all on the board or paper.
The packaging of the invention also shows a good perforation resistance, a good stiffness and a nice gloss. Moreover, thanks to the low coefficient of friction of the film, it is possible to work it at high speed in a packaging machine.
The packaging of the invention can find use in food packagings. It can find use in the packaging of solid food like chocolates, biscuits, and also in liquid food like fruit juices, beverages, soups, oils, water, alcohols.